751.9 Bridge Seismic Design - Revision history

Hoskir: updated per RR3868

2024-07-19T18:48:39Z

updated per RR3868

Hoskir: Hoskir moved page 751.9 LFD Seismic to 751.9 Bridge Seismic Design: renamed per RR3868

2024-07-19T18:45:36Z

Hoskir moved page 751.9 LFD Seismic to 751.9 Bridge Seismic Design: renamed per RR3868

← Older revision	Revision as of 13:45, 19 July 2024
(No difference)

Smithk: updated links

2022-06-01T16:21:53Z

updated links

← Older revision		Revision as of 11:21, 1 June 2022
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	====751.9.3.1.4 Concrete Shear Blocks====		====751.9.3.1.4 Concrete Shear Blocks====
	'''For LRFD, see [[751.22 Prestressed Concrete I Girders#751.22.3.14 Concrete Shear Blocks\|EPG 751.22.3.14 Concrete Shear Blocks]] for Concrete Shear Blocks design'''		'''For LRFD, see [[751.22 Prestressed Concrete I Girders#751.22.3.13 Concrete Shear Blocks\|EPG 751.22.3.13 Concrete Shear Blocks]] for Concrete Shear Blocks design'''

	Concrete shear blocks are used when 4 anchor bolts per bearing are insufficient, or for preventing loss of support on beams and stub bent footings. Design shear keys as specified in AASHTO 8.16.6.4. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The following dimensions and sizes are for rough guidelines only and may be		Concrete shear blocks are used when 4 anchor bolts per bearing are insufficient, or for preventing loss of support on beams and stub bent footings. Design shear keys as specified in AASHTO 8.16.6.4. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The following dimensions and sizes are for rough guidelines only and may be
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	A<sub>cv</sub> = area of concrete block at the shear plane, sq. inches		A<sub>cv</sub> = area of concrete block at the shear plane, sq. inches

	'''Example:''' An example of a shear block details can be found in [[751.22 P/S Concrete I Girders#751.22.3.14 Concrete Shear Blocks\|EPG 751.22.3.14]].		'''Example:''' An example of a shear block details can be found in [[751.22 P/S Concrete I Girders#751.22.3.13 Concrete Shear Blocks\|EPG 751.22.3.13]].

	====751.9.3.1.5 Concrete End Diaphragms====		====751.9.3.1.5 Concrete End Diaphragms====

Smithk: /* 751.9.3.1.4 Concrete Shear Blocks */

2022-05-17T17:30:09Z

751.9.3.1.4 Concrete Shear Blocks

← Older revision		Revision as of 12:30, 17 May 2022
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	====751.9.3.1.4 Concrete Shear Blocks====		====751.9.3.1.4 Concrete Shear Blocks====
			'''For LRFD, see [[751.22 Prestressed Concrete I Girders#751.22.3.14 Concrete Shear Blocks\|EPG 751.22.3.14 Concrete Shear Blocks]] for Concrete Shear Blocks design'''

	Concrete shear blocks are used when 4 anchor bolts per bearing are insufficient, or for preventing loss of support on beams and stub bent footings. Design shear keys as specified in AASHTO 8.16.6.4. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The following dimensions and sizes are for rough guidelines only and may be		Concrete shear blocks are used when 4 anchor bolts per bearing are insufficient, or for preventing loss of support on beams and stub bent footings. Design shear keys as specified in AASHTO 8.16.6.4. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The following dimensions and sizes are for rough guidelines only and may be
	altered to fit specific situations:		altered to fit specific situations:

	Concrete block dimensions:		Concrete shear block dimensions:

	L = Length shall extend all the way across the beam (for ease of forming), oriented parallel to centerline of roadway.		L = Length shall extend all the way across the beam (for ease of forming), oriented parallel to centerline of roadway.
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	Spacing = Spacing of hairpin shear bars as required to provide the required steel area, with 6" minimum to 12" maximum. The maximum edge distance in the direction of the spacing = half of reinforcement spacing.		Spacing = Spacing of hairpin shear bars as required to provide the required steel area, with 6" minimum to 12" maximum. The maximum edge distance in the direction of the spacing = half of reinforcement spacing.

	<math>V_{dem} = \frac{F_T}{R\times \phi \times N_B} </math> = demand shear per block, kips/block where:		<math>V_{dem} = \frac{F_T}{R\times \phi \times N_B} </math> = demand shear per block, kips/block

			:where:

	:F<sub>T</sub> = transverse component of total horizontal seismic force demand at the bent, normal to the centerline of the roadway, kips. Both seismic load cases, Case 1 = L+0.3T and Case 2 = 0.3L+T, must be satisfied.		:F<sub>T</sub> = transverse component of total horizontal seismic force demand at the bent, normal to the centerline of the roadway, kips. Both seismic load cases, Case 1 = L+0.3T and Case 2 = 0.3L+T, must be satisfied.

Smithk: /* 751.9.3.1 Connection Design */ Per BR, clarified bearing anchor bolt, dowel bar, and shear block design.

2022-05-11T19:28:53Z

751.9.3.1 Connection Design: Per BR, clarified bearing anchor bolt, dowel bar, and shear block design.

Show changes

Smithk: Per BR, updated several links

2022-01-11T16:08:04Z

Per BR, updated several links

Show changes

Smithk: /* 751.9.3.1.1 Anchor Bolts */ minor corrections

2021-12-06T19:58:30Z

751.9.3.1.1 Anchor Bolts: minor corrections

← Older revision		Revision as of 14:58, 6 December 2021
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	::At intermediate bents, F<sub>H</sub> = <math>\sqrt {(\sum V_L)^2 + (\sum V_T)^2}</math>, where:		::At intermediate bents, F<sub>H</sub> = <math>\sqrt {(\sum V_L)^2 + (\sum V_T)^2}</math>, where:

	:::<math>\~~Epsilon~~ V_L</math> = summation of top of column longitudinal shears at all columns		:::<math>\sum V_L</math> = summation of top of column longitudinal shears at all columns

	:::<math>\~~Epsilon~~ V_T</math> = summation of top of column transverse shears at all columns		:::<math>\sum V_T</math> = summation of top of column transverse shears at all columns

	::At end bents, use the same formula as above, except substitute the abutment shears in place of the top of column shears.		::At end bents, use the same formula as above, except substitute the abutment shears in place of the top of column shears.
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	For shear stress, design the bolt diameter to satisfy the allowable stress as shown below (f<sub>v</sub> < F<sub>v</sub>). Limit the number of bolts per bearing to four by adding concrete shear blocks when required.		For shear stress, design the bolt diameter to satisfy the allowable stress as shown below (f<sub>v</sub> < F<sub>v</sub>). Limit the number of bolts per bearing to four by adding concrete shear blocks when required.

	:<math>f_v = {frac{P}{A} \le F_v}</math>		:<math>f_v = \frac{P}{A} \le F_v</math>

	f<sub>v</sub> = actual shear stress on the bolt, ksi		f<sub>v</sub> = actual shear stress on the bolt, ksi
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	::::::4.00 sq. in. for 2-1/2" diam. bolt		::::::4.00 sq. in. for 2-1/2" diam. bolt
	F<sub>t</sub> = allowable tensile stress = 68 ksi		F<sub>t</sub> = allowable tensile stress = 68 ksi


	====751.9.3.1.2 Dowel Bars====		====751.9.3.1.2 Dowel Bars====

Smithk: Updated website link for increased security

2021-10-25T14:51:02Z

Updated website link for increased security

← Older revision		Revision as of 09:51, 25 October 2021
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	'''1)''' From the boring data and the bridge profile plot, determine the SPT blowcounts along the pile length.		'''1)''' From the boring data and the bridge profile plot, determine the SPT blowcounts along the pile length.

	'''2)''' Determine the soil properties required for the SPILE computer program or any other computer programs based on the methods presented by Nordlund (1963,1979), Thompson (1964), Meyerhoff (1976), Cheney and Chassie (1982), and Tomlison (1979,1985). Assume that the groundwater table is at the [~~http~~://epg.modot.org/index.php?title=750.3_Bridges#750.3.2.4.1_Normal_Water_Surface_Elevation Normal Water Surface Elevation].		'''2)''' Determine the soil properties required for the SPILE computer program or any other computer programs based on the methods presented by Nordlund (1963,1979), Thompson (1964), Meyerhoff (1976), Cheney and Chassie (1982), and Tomlison (1979,1985). Assume that the groundwater table is at the [https://epg.modot.org/index.php?title=750.3_Bridges#750.3.2.4.1_Normal_Water_Surface_Elevation Normal Water Surface Elevation].

	'''3)''' Run the SPILE program (Urzua,1993) or other programs using the methods described above to determine Q<sub>b</sub> and Q<sub>f</sub>.		'''3)''' Run the SPILE program (Urzua,1993) or other programs using the methods described above to determine Q<sub>b</sub> and Q<sub>f</sub>.

Smithk: updated links

2021-06-10T15:00:10Z

updated links

← Older revision		Revision as of 10:00, 10 June 2021
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	====751.9.3.1.2 Dowel Bars====		====751.9.3.1.2 Dowel Bars====

	Dowel bars connect standard concrete diaphragms and beams on concrete girder bridges (standard fixed diaphragms are those with beam stirrups NOT extending up into the diaphragm). Dowel bars are standard rebars designed using Allowable Stress Design and an allowable overstress of 33%. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The length of dowel bars is as shown in [[751.22 P/S Concrete I Girders#751.22.3.15 Dowel Bars\|EPG 751.22.3.15 Dowel Bars]]. For a calculated seismic vertical reaction or an anticipated foundation settlement resulting in a net tensile reaction, use the development length of dowel bars into beam and into diaphragm based on dowel bar size.		Dowel bars connect standard concrete diaphragms and beams on concrete girder bridges (standard fixed diaphragms are those with beam stirrups NOT extending up into the diaphragm). Dowel bars are standard rebars designed using Allowable Stress Design and an allowable overstress of 33%. Design forces are as specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. The length of dowel bars is as shown in [[751.22 P/S Concrete I Girders#751.22.3.13 Dowel Bars\|EPG 751.22.3.13 Dowel Bars]]. For a calculated seismic vertical reaction or an anticipated foundation settlement resulting in a net tensile reaction, use the development length of dowel bars into beam and into diaphragm based on dowel bar size.

	'''Shear Stress'''		'''Shear Stress'''
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	A<sub>cv</sub> = area of concrete block at the shear plane, sq. inches		A<sub>cv</sub> = area of concrete block at the shear plane, sq. inches

	'''Example:''' An example of a shear block design can be found in [[751.22 P/S Concrete I Girders#751.22.3.17 Shear Blocks\|EPG 751.22.3.17]].		'''Example:''' An example of a shear block design can be found in [[751.22 P/S Concrete I Girders#751.22.3.15 Shear Blocks\|EPG 751.22.3.15]].

	====751.9.3.1.5 Concrete End Diaphragms====		====751.9.3.1.5 Concrete End Diaphragms====

Smithk: /* 751.9.3.1 Connection Design */ Per BR, corrected bolt specs to latest ASTM, clarified welding inspection procedures and other miscellaneous items.

2020-08-18T15:27:46Z

751.9.3.1 Connection Design: Per BR, corrected bolt specs to latest ASTM, clarified welding inspection procedures and other miscellaneous items.

← Older revision		Revision as of 10:27, 18 August 2020
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	===751.9.3.1 Connection Design===		===751.9.3.1 Connection Design===

	'''Seismic Performance Categories A, B, C, D''''		'''Seismic Performance Categories A, B, C, D'''

	Seismic design forces can be considered either service loads or factored loads with a factor of 1.0. Load Factor Design (LFD) is to be used wherever possible. However, Allowable Stress Design (ASD) is still allowed when LFD would be difficult to apply. Connections must be designed for seismic forces in all four Seismic Performance Categories (A, B, C and D). For design of		Seismic design forces can be considered either service loads or factored loads with a factor of 1.0. Load Factor Design (LFD) is to be used wherever possible. However, Allowable Stress Design (ASD) is still allowed when LFD would be difficult to apply. Connections must be designed for seismic forces in all four Seismic Performance Categories (A, B, C and D). For design of
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	'''Seismic Performance Category A'''		'''Seismic Performance Category A'''

	Minimum horizontal design force in each restrained direction for ~~connectionsin~~ SPC A is as described in AASHTO Division I-A, Section 5.2.		Minimum horizontal design force in each restrained direction for connections in SPC A is as described in AASHTO Division I-A, Section 5.2.

	A seismic analysis is not required in SPC A, so do not use R=0.8 in SPC A. Use R=1 instead.		A seismic analysis is not required in SPC A, so do not use R=0.8 in SPC A. Use R=1 instead.
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	====751.9.3.1.1 Anchor Bolts====		====751.9.3.1.1 Anchor Bolts====

	Anchor bolts are used on bearings with sole plates. Design anchor bolts for flexure, shear and axial forces. Design forces are specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. ~~Design strengths~~ are ~~from AASHTO Table 10~~.~~56A, LFD, for ASTM A325~~ bolts~~, unless otherwise noted~~.		Anchor bolts are used on bearings with sole plates. Design anchor bolts for flexure, shear and axial forces. Design forces are specified in AASHTO Div. I-A, Sections 3.6, 3.7, 5.2, 6.2 or 7.2. Anchor bolts shall be ASTM F1554 Grade 55, unless higher grade anchor bolts are required to meet design requirements. Grade 105 bolts shall not be used in applications where welding is required.

	'''Flexural Stress'''		'''Flexural Stress'''
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	::S = Section modulus for the bolt = <math>\frac{\pi D^3}{32}</math>, cubic inches.		::S = Section modulus for the bolt = <math>\frac{\pi D^3}{32}</math>, cubic inches.
	::D = bolt diameter, inches. The gross bolt diameter may be used because the bolt is unthreaded in the flexural zone.		::D = bolt diameter, inches. The gross bolt diameter may be used because the bolt is unthreaded in the flexural zone.
	::F<sub>b</sub> = (overstress factor=1.5)0.55(F<sub>y</sub>=50 ksi) = 41.25 ksi		::F<sub>b</sub> = (overstress factor=1.5)0.55(F<sub>y</sub>=55 ksi) = 45.4 ksi

	'''Shear Stress'''		'''Shear Stress'''
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	:<math>f_v = {frac{P}{A} \le F_v}</math>		:<math>f_v = {frac{P}{A} \le F_v}</math>

	f<sub>v</sub> = actual shear stress on the bolt, ksi		f<sub>v</sub> = actual shear stress on the bolt, ksi

	P = the design shear force per bolt, kips/bolt = <math>\frac{F}{n_bN_gR}</math>,		P = the design shear force per bolt, kips/bolt = <math>\frac{F}{n_bN_gR}</math>,
	: where the definitions are the same as in the flexural stress section.		: where the definitions are the same as in the flexural stress section.
	F<sub>v</sub>= allowable shear stress per bolt, ksi = (28.~~5 ksi~~)(f1)(f2)*(f3)
			F<sub>v</sub>= allowable shear stress per bolt, ksi = 1.5(0.625Fub)(f1)(f2)(f3)/(F.S.)
	:where:		:where:
	:28.~~5 ksi~~ = 1.~~5x19 ksi, where 19 ksi is from AASHTO Table 10~~.32.3B		:Fub = 75 ksi = minimum tensile strength of bolt
			:(F.S.) = 3.75 as back-calculated from LRFD Eq. 6.13.2.12-1 & 6.13.2.2-2 with an assumed load factor of 1.4 and <math>\phi_s</math> = 0.75.
	:f1 = 0.875 for bolts > 1" diameter, 1.0 for bolt diameters ≤ 1"		:f1 = 0.875 for bolts > 1" diameter, 1.0 for bolt diameters ≤ 1"
	:f2 = 1.25 for threads not in the shear plane (use)		:f2 = 1.25 for threads not in the shear plane (use)
	:f2 = 1.0 for threads in the shear plane (don't use)		:f2 = 1.0 for threads in the shear plane (don't use)
	~~:f3 = 0.8 when distance between outermost bolts > 50" (rare)~~		:f3 = 1.0
	:f3 = 1.0 ~~when distance between outermost bolts < 50" (usual case).~~		:For most anchor bolts, Fv = 1.50.625750.8751.25/3.75 = 20.5 ksi.
	:For most anchor bolts, Fv = 28.50.8751.25 = 31.17 ksi.
	A = <math>\frac{\pi D^2}{4}</math> = Area of bolt, square inches		A = <math>\frac{\pi D^2}{4}</math> = Area of bolt, square inches

	D = The gross bolt diameter, because bolt is unthreaded in the shear zone.		D = The gross bolt diameter, because bolt is unthreaded in the shear zone.

	'''Axial Stress'''		'''Axial Stress'''

	For axial stress, design the bolt diameter to satisfy the allowable tensile stress as shown below. For further information about vertical restrainers (hold-down devices), see [[751.9 LFD Seismic#751.9.3.1.3 Restrainers\|EPG 751.9.3.1.3]].		For axial stress, design the bolt diameter to satisfy the allowable tensile stress as shown below. For further information about vertical restrainers (hold-down devices), see [[751.9 LFD Seismic#751.9.3.1.3 Restrainers\|EPG 751.9.3.1.3]].

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	::::::4.00 sq. in. for 2-1/2" diam. bolt		::::::4.00 sq. in. for 2-1/2" diam. bolt
	F<sub>t</sub> = allowable tensile stress = 68 ksi		F<sub>t</sub> = allowable tensile stress = 68 ksi


	====751.9.3.1.2 Dowel Bars====		====751.9.3.1.2 Dowel Bars====